This application claims the priority of Application No. 102 45 032.3, filed Sep. 26, 2002, in Germany, the disclosure of which is expressly incorporated by reference therein.
The present invention relates to vehicles with open transmission lines which, particularly when cornering, in the limit range at the change-over to an oversteering, reach high yaw velocities as well as high yaw accelerations. These yaw velocity or yaw accelerations require the driver to have a high degree of driving skill. For avoiding critical situations, these vehicles are often designed from the start to be clearly understeered.
German Patent Document DE 198 30 561 C2 has, a vehicle handling control for preventing a swerving and/or cross-wind deviation movement of a vehicle and particularly a vehicle handling control device for controlling the brake system of a vehicle. In the case of this known system, a selected wheel or several selected wheels are braked in a controlled manner in order to counteract a rise of the deviation of the actual yaw velocity detected by way of a yaw velocity sensor from a desired yaw velocity estimated from the steering angle and the vehicle speed. The system intervenes when the deviation is greater than a certain control value. Prior art discloses a device for appropriate control of vehicle handling based on an improved estimation of the deviation of the actual yaw velocity detected by way of a yaw velocity sensor from the desired yaw velocity estimated from the steering angle and the vehicle speed.
The present invention of the lateral correction describes a system for improving driving dynamics, which can be used easily and rapidly, for a control strategy for the longitudinal clutch and/or the main-axle lateral lock in the case of all-wheel systems or also of the controllable lateral lock of vehicles with single axle drives.
According to the present invention, the dampering of the yawing motion is increased by influencing the torque distribution between the axles and/or the change of the locking value at the lateral lock. This results in the stabilization of the vehicle.
Advantageously, the required input quantities for the method according to the invention already exist in a vehicle based on modern technology, and the signals of the sensors or the information existing in the data bus only have to be read out by the control unit. Quantities already known in the vehicle are the yaw angle, the yaw angle velocity, the yaw angle acceleration or the lateral acceleration and the driving direction desired by the driver which is defined, for example, by the steering angle. Complicated additional calculations are not required because all these data are already present in the vehicle in a processed manner and only the corresponding data exchange has to take place.
It is another advantage that the control strategy according to the invention can be used in the case of an all-wheel drive with longitudinal clutches, in the case of an all-wheel drive with controllable hang-on systems, in the case of an all-wheel drive with a fixed distribution and a controllable longitudinal lock, in the case of an all-wheel drive with a controllable rear-axle lateral lock as well as in the case of single-axle driven vehicles with a controllable lateral lock.
In all these methods, the required clutch torque is a function of the driving speed, the driving direction desired by the driver and the actual driving direction change of the vehicle. The value for the locking torque resulting from these input quantities can be applied by way of several characteristic curves or characteristic diagrams and by means of separate variables for the longitudinal and lateral lock and can be correspondingly filed in the control unit. In this case, the application advantageously takes place in a manner which is individually adapted to the vehicle type and the motorization.
Finally, it is advantageous, according to the present invention, to provide a response threshold for the intervention of the control strategy. Here, a reference value can be defined which indicates the permissible deviation of the actual and the desired value.
Other objects, advantages and novel features of the present invention will become apparent form the following detailed description of the invention when considered in conjunction with the accompanying drawings.